Surgical procedures can act to seriously weaken the body of the patient. Major surgeries are in fact an extreme assault upon the body which in turn affects the immune response system of the patient. This in turn increases the risk of post-operative infection. Such post-operative infection has a significant effect upon the survival rate after major surgery.
Further many patients prior to surgery are already in a particularly debilitated condition. Many patients who have digestive track problems which require surgery have not been able to ingest sufficient calories to maintain body weight and keep themselves in a healthy condition. Accordingly, many patients require a pre-operative stay to obtain either an enteral or parenteral diet to increase body weight and improve their health.
It has been shown that diet can affect the immune response system after major assaults to the body. For example, The Importance of Lipid Type in the Diet After Burn, Anals. of Surgery, Vol. 204, No. July, 1, 1986 reports that the lipids contained in a diet have an effect on the immune response system in burn patients. Specifically, it indicated that a diet high in omega 6 fatty acids such as linoleic acid have a significant immunosupressive effect. On the other hand, diets high in omega 3 fatty acids improve the immune response. In "The Effect of Dietary Unsaturated Fatty Acids and Indomethacin on Metabolism and Survival after Burn" indicates that excessive dietary polyunsaturated linoleic acid may influence immunocompetence after burn. Accordingly, all indications are that omego 6 fatty acids have a immunosuppressive effect.